The overall objectives of the proposed research are to acquire basic information on Wuchereria bancrofti and Brugia spp., lymphatic-dwelling filarial parasites of man and animals. The complete development of W. bancrofti in monkeys now provides opportunities for a wide range of studies in the laboratory on a parasite that until recently was thought only to occur in man. Characterization of the morphologic and biologic aspects of the parasite in primates will be stressed, in particular, details on the developmental cycle and the course of infection. Further passage of W. bancrofti to various species of macaque monkeys will be attempted and efforts will also be continued to adapt this parasite to a rodent host. In addition to the efforts with W. bancrofti the Mongolian jird, Meriones unquiculatus, a highly successful rodent host for species of the genus Brugia, will be utilized to provide basic information on the immune response of the vertebrate host to filarial infections. Extensive use will be made of a recently developed syngeneic strain of jird to study the role of the macrophage in the immune response of this host to infection with B pahangi.